Didion | Sand Casting Processing

Many foundries have solved the bottleneck problem in the cleaning and finishing departments by first updating their shakeout system. The amount of sand carryover as well as the sand adhering to the castings is the single biggest factor relating to shotblast costs (labour to operate, shot consumption, energy consumption, replacement wear parts, and maintenance time).

By eliminating the sand from going into the casting cleaning department and keeping it in the sand system where it belongs, the benefits go right to the bottom line. In addition to saving on all the above shotblast cost, other savings include less wear on the dust collectors, less waste streams, no airborne silica dust, and less clean up time.

When the castings are pre-cleaned in the shakeout system, the cleaning/finishing bottleneck is eliminated. Couple the pre-cleaning with casting cooling and the production flow is really streamlined.

Cleaning Department Relief
Having cleaned gates, runners, and sprue from the shakeout department that go directly to the melt department greatly relieves the cleaning department bottleneck. If the gates, runners, and sprue are too great a burden to shot blast, then the melting department faces excessive slag build up, reduced furnace lining life, and lower melting efficiency.

The savings in the melting department alone can easily justify the need to have clean returns directly from the shakeout department. Cleaner melting, finishing, and shakeout areas all add up to a better and safer workplace.

Saint Gobain Pipelines, Sinclair Works in Telford, England, improved its shakeout and finishing operations by installing a Didion Rotary Media Drum to eliminate shot blasting altogether. The Mark 5 Rotary Media Drum processes sand and castings from a DISA vertically parted moulding line.

The sand is separated from the castings and is screened twice to minus 9mm in the Didion. All the metallics are thoroughly cleaned by a recirculating bed of prismatoid media, which also protects and cools the castings. Upon discharging from the drum, the castings are submerged into a water quench for final cooling. The clean and cooked castings are automatically conveyed to the grinding stations in the finishing department. The clean gates, runners, and sprue go directly back to the melting department.

Successful Streamlining
This streamlined approach has been so successful that the foundry has ordered Didion's latest Mark 5 Series Rotary Media Drum for installation this summer 2003. The Mark 5 design is even more robust with several new features such as; external sand screening, automatic chain tensioner, split pillow block design with quick change bearing inserts, duplex chain, thicker liners with contoured rifling, cast in dam retention rings, and a self relieving tapered media separation chamber for fragile castings.

Several other foundries in the UK that have benefited from the new Mark 5 Series Machines include Castings PLC, Vald Birn, William Lee, and Triplex Foundry.

Combining sand casting separation, dual sand screening, plus casting cleaning and cooling, has proved so successful that paybacks are calculated in four to five months. The foundry also has less capital equipment to purchase, install, and maintain. Less equipment means less dust collection requirements and less daily energy consumption. Currently Didion International has the New Mark 5 Series Rotary Media Drum in 42 countries worldwide.

The machines are custom designed to handle aluminum, brass, bronze, ductile, grey, and steel castings. Greensand, shell, lost foam, and no bake foundries have all benefited from this unique patented approach.

Multiple Benefits
United Machine & Foundry in Winona, Minnesota, USA, installed a new Didion Mark 5 Series Machine and UMF's director of operations, Steve Renk, describes the benefits the company has achieved.

"With the installation of our new MK5 Rotary Media Drum, we have improved three facets of the UMF operation-safety, quality, and productivity. Improvements in these areas are critical to our ability to succeed in the ever competitive foundry industry. The Didion gives us an advantage over competitors!" he says.

"Prior to installing our new equipment, we operated a vibratory shakeout system," continues Renk. "A man running this piece of equipment was pretty much sentenced to work in hell. We lost a number of employees over the years from the simple fact that the job was just too barbaric. Standing over a vibrating shakeout, trying to hook castings and place them in tote boxes is difficult and is compounded by dust, steam, and heat. By installing the Mark 5, we have eliminated a safety hazard."

Renk says the company has realised quality improvements too. "The Rotary Media Drum's ability to blend hot and cool sand has also benefited our sand system. With the vibratory shakeout, the sand storage system had layers of hot sand on top of layers of cool sand, making the compactability of the sand difficult to control. The new system has helped reduce big swings in sand temperatures, thus allowing our compactability controller to run much more efficiently."

"Productivity gains and reduced costs have proved to be an added bonus for UMF operations. Many of the castings that we produce are no longer shotblast," says Renk. "UMF has reduced the man hours in shotblast and reduced operating hours on the maintenance intensive shotblast machines, which has allowed us to use production and maintenance personnel more effectively. We have significant annual savings from reductions in labour, sand disposal costs, shot purchases, accidents, maintenance/repair costs."

Modernised Post Casting Operations
World class casting producers in the USA such as Waupaca Foundries, Wescast, Intermet, Grede, and Victaulic have modernised their shakeout/cleaning operations with Mark 5 drums. Ductile iron castings with difficult/tough gating systems for workers trying to remove manually are automatically de-gated in the Didion. The labour savings for this difficult and dangerous job alone have cost justified to modernise the shakeout department.

Didion says that it has yet to find any capital improvement a foundry can make that offers the payback like the Mark 5.

Approximately 20% of the cost to produce a 10kg ductile casting comes from shakeout, fettling, and cleaning. By combining shakeout, sand screening, casting cleaning, and casting cooling, ferrous foundries can easily reduce these costs by 50% and save $80.00/ton, claims the company.